As scientists eagerly await the arrival of NASA’s New Horizons spacecraft at the Pluto system, they are looking to other icy bodies that could have similarities to the dwarf planet. Among them is the mysterious world of Triton, the largest moon of Neptune.
One way that scientists hope to learn more is simply by looking at the features of each of the objects, comparing and contrasting them. That will be made slightly easier with the arrival of a new map of Triton, based on data gathered by NASA’s Voyager 2 spacecraft as it flew by 25 years ago.
“Scientists think Triton is a Kuiper Belt Object captured by Neptune’s gravity millions of years ago. It shares many similarities with Pluto, the best known world of the Kuiper Belt,” wrote NASA in a description of Triton for its website about the Solar System.”Like our own moon, Triton is locked in synchronous rotation with Neptune—one side faces the planet at all times. But because of its unusual orbital inclination both polar regions take turns facing the Sun.”
Pluto’s surface is still somewhat of a mystery to scientists, because the world is so distant and so small. The best available images from the Hubble Space Telescope, which has looked at the dwarf planet from time to time over the years, show a blur.That said, scientists have been able to detect carbon dioxide, methane, nitrogen and carbon monoxide on both Pluto’s surface and Triton, showing that the two worlds may have had a similar origin. But there are also vast differences.
When Triton was captured by Neptune, the interaction likely sparked vast tidal heating within its interior, which would have produced surface features (such as fractures) that would not be on Pluto’s.Another feature of Pluto that is different than Triton is its distance from the Sun (it takes about 248 years to complete one circuit) and its elliptical orbit, which sometimes brings it within Neptune’s orbit. As Pluto draws slightly closer to the Sun, the heat of the closest star affects its surface, NASA noted.
“Since its orbit is so elliptical, when Pluto is close to the Sun, its surface ices thaw, rise and temporarily form a thin atmosphere,” NASA wrote.”Pluto’s low gravity (about six per cent of Earth’s) causes the atmosphere to be much more extended in altitude than our planet’s atmosphere. Pluto becomes much colder during the part of each orbit when it is traveling far away from the Sun. During this time, the bulk of the planet’s atmosphere is thought to freeze.
“Pluto is also replete with moons, with five known to date. Most of these were discovered while New Horizons was either being planned, or sent on its way to the system. Triton, being a moon of Neptune itself, has no known satellites.New Horizons will fly by Pluto on July 14, 2015 and likely sail on to investigate a Kuiper Belt object. Scientists are now scanning Hubble data to see which would be a good world to look at next.